The invention relates to an expansible fixing plug having an internal bore passing right through the plug body into which an expansion bolt in the form of a nail or screw is to be driven, and to a method for the manufacture thereof from metal.
Expansible fixing plugs of that kind made of plastics material are already sufficiently well known. The internal bore of these expansible fixing plugs generally runs axially parallel and tapers towards the leading end of the plug. In the region of the tapering internal bore, these expansible fixing plugs have longitudinal slits to allow expansion as the expansion bolt is driven in. In order to achieve a satisfactory expansion, in particular also in soft building materials, the tapering internal bore terminates in a cleft, the internal width of which corresponds to the slit width. This very sudden taper of the internal bore requires a high insertion resistance which, when using the known fixing plugs in hard building materials, may in some circumstances prevent the expansion bolt from being driven fully home. Moreover, because the expansion is effective only for a part of the length of the expansible fixing plug, a holding force commensurate with the high insertion resistance is not achieved. Such an expansion principle is therefore also little suited to cavity bricks, since stress peaks are able to occur in individual webs of the cavity bricks as a result of the uneven distribution of the expansion force, and these stress peaks lead to destruction of the brick. Moreover, in the known expansible fixing plugs the central and axially parallel arrangement of the internal bore and longitudinal slits produces a preferred expansion direction for the entire length of the fixing plug, which firstly produces a cleaving effect and secondly, despite high insertion resistances, does not allow stress to be distributed uniformly in the drilled hole, which would give rise to high holding forces.